The present invention relates to a recording apparatus including an inkjet head that ejects ink to a recording medium.
An inkjet recording apparatus is widely used. The inkjet recording apparatus is configured to supply ink from an ink cartridge to an inkjet recording head, and eject ink droplets from the recording head onto a recording medium to record an image, character or the like.
Such an inkjet recording head is adopted not only a small-sized recording head for use in a home, small office or the like, but also for a large-sized recording head capable of printing onto a large recording medium having a width of 1 m or wider.
The inkjet recording apparatus includes a carriage on which the recording head is mounted. The carriage is configured to reciprocate across the recording medium in a widthwise direction. The recording head ejects ink onto the recording medium on a forward path and on a backward path. A position of the carriage is detected by reading a linear scale provided along a moving direction of the carriage using a sensor mounted on the carriage. Generally, a device referred to as a linear encoder is used.
The recording head has a lot of small holes, i.e., nozzles. There are cases where the nozzle may be clogged with thickened ink, dust or the like. When the nozzle is clogged, ink is not ejected from the clogged nozzle, and therefore a stripe pattern may be formed in a recorded image.
In order to prevent non-ejection from the nozzle Japanese Laid-Open Patent Publication No. 10-138513 discloses processing performed before recording. In the processing, a test pattern is recorded using respective nozzles, the recorded test pattern is read by an optical sensor to thereby determine a non-ejection nozzle, and an ejection signal is sent to the non-ejection nozzle to forcedly eject ink.
However, in the related art, for example, when the nozzles are arranged at a density of 400 dpi, a nozzle pitch is 63 μm, and a line recorded using one dot has a width of approximately 150 to 200 μm. The sensor has a wide detection range which may include both of a recorded portion and a non-recorded portion. Therefore, when light color ink is used, a contrast between the test pattern and the recording medium is low, and therefore the test pattern may not be accurately detected, i.e., misdetection may occur. Further, the test pattern need be determined in consideration of the detection range of the sensor, a conveyance accuracy of the recording medium, and a relative movement accuracy of the recording medium and the sensor. Therefore, it is necessary to widen a line spacing of the test pattern, and therefore a recording area of the test pattern becomes large.